The invention relates generally to electric machine stators.
Stators of large electric machines, especially generators, are typically built with a standard number of keybars and two flanges. One flange is positioned at each end to mechanically couple the keybars and support the stator. The number of the keybars and sizes of the keybars and the flanges are designed mainly for meeting mechanical requirements of the stator.
For mechanical stability, keybars generally comprise magnetic or non-magnetic steel or steel alloys. Such materials are electrically conductive. Due to the keybars being situated in the vicinity of magnetic fields and being electrically conductive, adverse electromagnetic effects result and limit electric machine rating and performance.
Keybar voltage restricts the stator yoke (back iron) flux density. The main cause of keybar voltage is leakage flux that spills behind the stator core outer surface. If electromagnetic effects of the keybars can be reduced, electrical design engineers would have more freedom and fewer restrictions to further optimize the machine and thus be able to reduce the machine cost without sacrificing efficiency and reliability in a safe manner.
It would therefore be desirable to reduce keybar voltages in electric machines (and thus reduce adverse electromagnetic effects) without compromising the integrity of the electric machines.